1. Field of the Invention
The present invention relates to a transparent smart light source capable of adjusting an illumination direction, and more particularly to a transparent smart light source configured to adjust an illumination direction using a device capable of adjusting reflectance and transmittance.
2. Discussion of Related Art
After the advent of incandescent lamps and fluorescent lamps, light-emitting diodes (LEDs) have recently attracted attention. In the early stage, the LEDs have problems of low brightness and poor color characteristics. However, with the development of technology, the LEDs have been developed to have high efficiency and excellent color characteristics and put to practical use.
Light sources that are currently under active development after the LEDs are organic light-emitting diodes (OLEDs) that emit light using an organic semiconductor material. Since the OLEDs have a small thickness, small weight, and a rapid response speed, application to a backlight unit (BLU) of a liquid crystal display (LCD) as well as a general lighting device is under active development.
FIG. 1 is a schematic cross-sectional view of an OLED 100.
Referring to FIG. 1, the OLED 100 is a self light-emitting device in which holes injected from an anode electrode and electrons injected from a cathode electrode 170 are combined to form excitons at an organic light-emitting layer 150, and the excitons emit light while releasing energy.
When both of the anode electrode 130 and the cathode electrode 170 are transparent electrodes, it is possible to fabricate a transparent OLED capable of bottom emission and top emission both. Lately, a smart light source in which such a transparent OLED is integrated with glass or windows is under development.
However, a transparent OLED emits light in two opposite directions. Thus, when a surface light source is implemented using a transparent OLED, even if light emission is needed in only one direction, light is emitted unnecessarily in the other direction and optical loss occurs.
For example, when a transparent OLED is applied to a window, light is emitted to the inside and outside of a building. Here, the light emitted to the outside fails to contribute indoor lighting, and causes the dissipation of energy.